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need feedback about autoX spring rates for AGX front struts

CadVetteStang

CadVetteStang

New member
I'm rethinking my spring rate and lowering.

This is a daily driver that will see autocross once per month. I will be using the AXGs for the 97-03 GP, however my Eldo is 50 lbs. Heavier at each front corner, has a 2.5" shorter wheelbase and 2% better f/r weight distribution.

The GP stock rate is 115 variable.(I hate not being able to find starting and ending rates on variable springs)
My stock Eldo rate is 135 linear.
I was going for variable springs rated at 416 to be cut to fit resulting in about a 525ish average rate. And a 1.5" to 2" drop... However, I'm reading that KYB recommends a maximum rate for the ACTs to be stock +50%·
That would be about 179.
For the GP.
If I go at 150% ofthe Eldo, I get about 202 (which is 175% of the GP rate.

KYB also recommend a 1"-1.5" drop .
I can live with that drop amount, but I don't know about 179-200 lb. springs.... seems like it would be too soft.
At the same time, I don't want to blow out the struts too quickly. I drive 24,000 miles per year.
I need real world feedback from GP autoXers on this.
Thanks .
 


Oh, wow! Talk about feeling deflated. I called KYB myself about this issue. They said they only rate their struts at 15% over stock rate , NOT 50%.
Now I don't know if I should even use them.
 
I can tell you one thing for sure, nobody here has put this much thought in the spring rate and what the struts can handle.

Mainly because they handle like a boat in stock form and lowering them with better suspension parts makes such a huge world of difference. That reason is likely why nobody does anything more or thinks about actual rates of springs for a better autox type situation.

Yes this post doesnt help answer your question at all, but it's still kinda true. I really have no idea what you'll want to use and it doesnt help that there are only a limited amount of aftermarket parts that work.
 
Fivefingerdeathpunch said:
I can tell you one thing for sure, nobody here has put this much thought in the spring rate and what the struts can handle.

Mainly because they handle like a boat in stock form and lowering them with better suspension parts makes such a huge world of difference. That reason is likely why nobody does anything more or thinks about actual rates of springs for a better autox type situation.
Click to expand...

This!


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I've found that 450 works beautifully on the gxp but that was with bilsteins, I think the bigger issue also is strut travel. Which can be mitigated with custom hats. I probably have the biggest investment in handling here besides james. My setup now:

Tubular lcas 34mm sway home made coilovers on agx shocks now. Full spherical bearing caster camber plates. Full bmr rear and stb front and rear
 
Thanks for the input. What spring rate do your AGXs have? And was that 450 constant or varible rate?
Have you found a vendor for the custom hats?
 


91parkave said:
I've found that 450 works beautifully on the gxp but that was with bilsteins, I think the bigger issue also is strut travel. Which can be mitigated with custom hats. I probably have the biggest investment in handling here besides james. My setup now:

Tubular lcas 34mm sway home made coilovers on agx shocks now. Full spherical bearing caster camber plates. Full bmr rear and stb front and rear
Click to expand...

I'll be up there soon enough

Guessing the billsteins reached there limit


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No, bilsteins held beautifully. Even with there old age. It way slimmed travel and a huge pothole i nailed that killed my passenger side.

Op, I keep my agx on the 3 or 4 settings and ride like that on 450 constant. Tophats you build yourself. This set i have now turbocharged400sbc built for me.
 
Good to know real world information. I'll keep my #416 variable rate springs for the AGX swap. I also found a shop that builds coilovers on the AGX struts for GM FWD cars . They use constant spring rates from #200 - #500 and have variable springs as an option.
I guess the KYB recomendation of stock + 15% is to keep them from getting into legal trouble if some home-grown racing project goes bad.

To use the springs I have selected, I have to change upper strut mounts and redrill the 3 holes in the strut tower. I'll adjust caster and camber when placing them. Hopefully, I will build 2 degrees too much negative camber and can then use camber adjustment bolts to correct... that would create a little more tire clearance at the strut.
 
Two shops actually.. Arraut and Intense.
But that mod is out of my budget and i will have too close of a tire to strut clearance to use a coilover.
 


a coilover should give more clearance than a stock strut/spring setup in most cases unless the caddy stuff is different than the wbody and has the two separate.

arraut would be the place to get them from if you did go that route. and if you're already modifying stuff, why not make your own? all the available options are a sleeve beat onto a trimmed down stock strut anyway. the only way you'd get something different is to modify the upper/lower mounts on a set of something like BC coilovers for a different application.
 
The Caddy strut is the same configuration as the 97-03 w-body strut (except for the swaybar end link mount bracket). Verticak tire clearance is no issue. The stock spring perch is above the tire tread giving inboard clearance all the way to the strut body.However, the coilover eluminates the stock perch and the springs extend downward a few inches farther. That eliminates the endlink btacket and places a coil between the strut and tire. To keep a 10" wide wheel with eleven inch wide tire under the front fender, it has to be a high positive offset. This makes coilovers a no go for me.As it is, I will need to fab a bracket to locate the endlink on the AGX strut.I have not yet looked into spacing the strut inboard at the knuckle.
 
CadVetteStang said:
The Caddy strut is the same configuration as the 97-03 w-body strut (except for the swaybar end link mount bracket). Verticak tire clearance is no issue. The stock spring perch is above the tire tread giving inboard clearance all the way to the strut body.However, the coilover eluminates the stock perch and the springs extend downward a few inches farther. That eliminates the endlink btacket and places a coil between the strut and tire. To keep a 10" wide wheel with eleven inch wide tire under the front fender, it has to be a high positive offset. This makes coilovers a no go for me.As it is, I will need to fab a bracket to locate the endlink on the AGX strut.I have not yet looked into spacing the strut inboard at the knuckle.
Click to expand...



http://www.wbodystore.com/suspension/performance-lowering-springs.html I do not know the spring rate for these, but I daily my gtp with these and agx struts and they are too stiff for the agx to handle, but it handles super flat and feels like it would be at home on an auto-x track if the control arms and the geometry of the suspension was better.
 


91parkave said:
What makes you think that lower springs are to stiff for agxs
Click to expand...

still getting about 1.5-2 rebounds after hitting an expansion joint on the highway. have anti-pogo washers, struts cranked up to 4. Maybe im just being a *****, but if I could have done it again I honestly would have gone with some softer springs. it handles super flat, with the stock sway bar. But the lack of ride quality is not worth it in a daily.
 
What setting are you running the struts on and how many miles are in them? If you have the struts tuned too soft to try making a stiff spring ride like a soft spring, then it won't dampen enough to stop the bounce. A worn strut will act the same way.
 
CadVetteStang said:
What setting are you running the struts on and how many miles are in them? If you have the struts tuned too soft to try making a stiff spring ride like a soft spring, then it won't dampen enough to stop the bounce. A worn strut will act the same way.
Click to expand...

the struts have about 20,000 miles on them. they are on the firmest setting currently, but have not been for the full 20k. I use my father's 98 z28 to compare most cars too, which is on strano springs, and koni shocks. That car has some amazing suspension tuning.
 
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